FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/rangecoder.h
Date: 2025-07-12 22:17:06
Exec Total Coverage
Lines: 50 50 100.0%
Functions: 5 5 100.0%
Branches: 18 18 100.0%
Line Branch Exec Source
1 /*
2 * Range coder
3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file
24 * Range coder.
25 */
26
27 #ifndef AVCODEC_RANGECODER_H
28 #define AVCODEC_RANGECODER_H
29
30 #include <stdint.h>
31
32 #include "libavutil/avassert.h"
33 #include "libavutil/intmath.h"
34
35 typedef struct RangeCoder {
36 int low;
37 int range;
38 int outstanding_count;
39 int outstanding_byte;
40 uint8_t zero_state[256];
41 uint8_t one_state[256];
42 uint8_t *bytestream_start;
43 uint8_t *bytestream;
44 uint8_t *bytestream_end;
45 int overread;
46 #define MAX_OVERREAD 2
47 } RangeCoder;
48
49 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
50 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
51
52 /**
53 * Terminates the range coder
54 * @param version version 0 requires the decoder to know the data size in bytes
55 * version 1 needs about 1 bit more space but does not need to
56 * carry the size from encoder to decoder
57 */
58 int ff_rac_terminate(RangeCoder *c, int version);
59
60 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
61
62 126118256 static inline void renorm_encoder(RangeCoder *c)
63 {
64
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 126118256 if (c->low - 0xFF01 >= 0x10000 - 0xFF01U) {
65 124941223 int mask = c->low - 0xFF01 >> 31;
66 124941223 *c->bytestream = c->outstanding_byte + 1 + mask;
67 124941223 c->bytestream += c->outstanding_byte >= 0;
68
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 126118169 for (; c->outstanding_count; c->outstanding_count--)
69 1176946 *c->bytestream++ = mask;
70 124941223 c->outstanding_byte = c->low >> 8;
71 } else {
72 1177033 c->outstanding_count++;
73 }
74
75 126118256 c->low = (c->low & 0xFF) << 8;
76 126118256 c->range <<= 8;
77 126118256 }
78
79 1702620 static inline int get_rac_count(RangeCoder *c)
80 {
81 1702620 int x = c->bytestream - c->bytestream_start + c->outstanding_count;
82
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 1702620 if (c->outstanding_byte >= 0)
83 1702155 x++;
84 1702620 return 8 * x - av_log2(c->range);
85 }
86
87 2056424387 static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit)
88 {
89 2056424387 int range1 = (c->range * (*state)) >> 8;
90
91 av_assert2(*state);
92 av_assert2(range1 < c->range);
93 av_assert2(range1 > 0);
94
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 2056424387 if (!bit) {
95 921740893 c->range -= range1;
96 921740893 *state = c->zero_state[*state];
97 } else {
98 1134683494 c->low += c->range - range1;
99 1134683494 c->range = range1;
100 1134683494 *state = c->one_state[*state];
101 }
102
103
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 2056424387 if (c->range < 0x100)
104 126095552 renorm_encoder(c);
105 2056424387 }
106
107 102455417 static inline void refill(RangeCoder *c)
108 {
109 102455417 c->range <<= 8;
110 102455417 c->low <<= 8;
111
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 102455417 if (c->bytestream < c->bytestream_end) {
112 102453674 c->low += c->bytestream[0];
113 102453674 c->bytestream++;
114 } else
115 1743 c->overread ++;
116 102455417 }
117
118 1694934594 static inline int get_rac(RangeCoder *c, uint8_t *const state)
119 {
120 1694934594 int range1 = (c->range * (*state)) >> 8;
121
122 1694934594 c->range -= range1;
123
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 1694934594 if (c->low < c->range) {
124 744223913 *state = c->zero_state[*state];
125
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 744223913 if (c->range < 0x100)
126 51489153 refill(c);
127 744223913 return 0;
128 } else {
129 950710681 c->low -= c->range;
130 950710681 *state = c->one_state[*state];
131 950710681 c->range = range1;
132
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 950710681 if (c->range < 0x100)
133 50966264 refill(c);
134 950710681 return 1;
135 }
136 }
137
138 #endif /* AVCODEC_RANGECODER_H */
139